Integrated unsupported slurry catalyst preconditioning process

ABSTRACT

A process for slurry hydroprocessing, which involves preconditioning a slurry catalyst for activity improvement in vacuum residuum hydroprocessing units Preconditioning the slurry catalyst raises its temperature, thereby reducing shock on the catalyst slurry as it enters the hydroprocessing reactor.

FIELD OF THE INVENTION

A process for slurry hydroprocessing, which involves preconditioning aslurry catalyst for activity improvement in vacuum residuumhydroprocessing units.

BACKGROUND OF THE INVENTION

Slurry catalyst compositions, means for their preparation and their usein hydroprocessing of heavy feeds are known in the refining arts. Someexamples are discussed below:

U.S. Pat. No. 4,710,486 discloses a process for the preparation of adispersed Group VIB metal sulfide hydrocarbon oil hydroprocessingcatalyst. Process steps include reacting aqueous ammonia and a Group VIBmetal compound, such as molybdenum oxide or tungsten oxide, to form awater soluble oxygen-containing compound such as ammonium molybdate ortungstate.

U.S. Pat. No. 4,970,190 discloses a process for the preparation of adispersed Group VIB metal sulfide catalyst for use in hydrocarbon oilhydroprocessing. This catalyst is promoted with a Group VIII Metal.Process steps include dissolving a Group VIB metal compound, such asmolybdenum oxide or tungsten oxide, with ammonia to form a water solublecompound such as aqueous ammonium molybdate or ammonium tungstate.

Slurry hydroprocessing processes frequently operate at highertemperatures than those at which slurries comprising catalysts aresynthesized and stored. For example, the slurry hydrocracking process ofU.S. Publication No. 20060054533 typically operates at a temperature ofat least 800° F., with a hydrogen pressure from about 1500 psi to about3500 psi. The slurry catalysts generally enter the reactor (or initialreactor, if more than one) of the vacuum residuum hydroprocessing unitat a temperature around 450° F. and a hydrogen pressure of about 400psi. This temperature and pressure differential shocks the highly activeslurry catalyst and promotes the production of coke. Coke productiondecreases the efficiency of conversion by this catalyst.

SUMMARY OF THE INVENTION

This application discloses a process for slurry hydroprocessing,particularly slurry hydrocracking, in which the slurry catalyst ispreconditioned prior to its entry into the reactor(s) of the vacuumresiduum slurry hydroprocessing process. Preconditioning the slurrycatalyst raises its temperature, thereby reducing shock on the catalystslurry as it enters the hydroprocessing reactor.

The process of this invention is summarized as follows:

A process for the hydroprocessing of heavy oils, having at least onereaction stage, said process comprising the following steps:

-   -   (a) contacting a hydrocarbon feed stream under slurry        hydroprocessing conditions with a hydrogen stream and a stream        comprising slurry hydroprocessing catalyst, in a vacuum residuum        slurry hydroprocessing unit, and recovering a product stream        along with a stream comprising spent slurry hydroprocessing        catalyst and unconverted hydrocarbon feed:    -   (b) passing the stream comprising spent slurry hydroprocessing        catalyst and unconverted hydrocarbon feed to a deoiling unit,        where it is combined with a solvent, products and gases then        being recovered, as well as a stream comprising spent slurry        catalyst;    -   (c) passing the: stream comprising spent slurry catalyst to a        metals recovery unit, where it is contacted with an ammonium        leach solution in order to recover ammonium sulfate and        compounds comprising Group VIII and Group VIB metals    -   (d) passing the compounds comprising Group VIII and Group VIB        metals to a catalyst synthesis unit, where they are contacted        with ammonia, hydrogen sulfide gas, hydrocarbon stream, hydrogen        and a small amount of water to create an active slurry catalyst        in oil, the oil comprising ammonium sulfate;    -   (e) passing the effluent of step (d) into a preconditioning unit        in order to increase the temperature and reduce shock on the        slurry catalyst, wherein the effluent is contacted with hydrogen        and is decomposed into hydrogen sulfide and ammonia, streams        which are removed from: the preconditioning unit;    -   (f) passing the effluent for step (e), which comprises the        active slurry catalyst in oil to storage or to a vacuum residuum        slurry hydroprocessing unit.

BRIEF DESCRIPTION OF THE FIGURE

The FIGURE illustrates the process disclosed in this invention forvacuum residuum slurry hydroprocessing using preconditioned slurrycatalyst.

DETAILED DESCRIPTION OF THE INVENTION

Stream 1, which comprises hydrogen, enters the vacuum residuum slurryhydroprocessing unit (VRHU) 10. Hydroprocessing processes which may beemployed in this invention include hydrocracking, hydrotreatinghydrodesulfurization, hydrodenitrification, and hydrodemetallization.Hydrocracking is the preferred process, however. Also entering VRHU 10is a feed stream 2 (vacuum residuum is a common feed), hydrogen stream 3and slurry catalyst stream 26 (which maybe admixed with Stream 3comprising water). The slurry hydrocracking process typically operatesat a temperature of at least 800° F., with a hydrogen pressure fromabout 1500 psi to about 3500 psi. The slurry catalysts followingpreconditioning, generally enters the reactor (or initial reactor, ifmore than one) of the vacuum residuum hydroprocessing unit at atemperature around 700° F. and a hydrogen pressure of about 2000 psi,

Products exit VRHU 10 through stream 55. Stream 4, the spent slurrycatalyst stream comprising unconverted oil, enters a deoiling unit 20where it is contacted by a solvent (stream 6) such as toluene or naphthain order to remove products and gases (stream 5). Deoiling involvessolid concentration and liquid removal, which may employ cross flowfiltration, centrifugation} drying and quenching steps.

Stream 7 comprises deoiled spent slurry catalyst. Stream 7 enters themetals recovery unit (MRU 30). Enriched air enters the MRU 30 throughstream 8. Stream 9 is a solvent suitable for metals extraction, such asketoxime. Through a series of solvent extractions and crystallizationsteps in MRU 30, the metals from the oil stream are recovered, alongwith a byproduct of ammonium sulfate (stream 27). Vanadium is removedthrough stream 11 as V₂O₅. Spent metals extraction solvent is removedthrough stream 12 and wastewater is removed through stream 13.

The Group VIII metal employed in the CASH process is often nickel.Nickel is recovered as a nickel sulfate stream (stream 14) and is passedto the catalyst synthesis unit (GSU 40). A portion of the nickel sulfatestream (stream 16) can be diverted to control the amount of nickelentering the catalyst synthesis unit (CSU 40). Recovered Group VI metalssuch as molybdenum, exit the MRU in stream 15. If the metal ismolybdenum, it is recovered as an ammonium dimolybdate stream (stream15) which is passed to the catalyst synthesis unit (CSU 40). A lighthydrocarbon or VGO (vacuum gas oil) (stream 17) enters into the catalystsynthesis unit (CSU 40) along with a small amount of water (stream 18).Stream 19 comprises hydrogen.

In the catalyst synthesis unit (CSU 40), conditions include atemperature in the range from 80° F. to 200° F., preferably in the rangefrom 100° F. to 180° F., and most preferably in the range from 130° F.to 160° F. Pressure is in the range from 100 to 3000 psig, preferably inthe range from 200 to 1000 psig, and most preferably from 300 to 600psig.

The ingredients are mixed in the CSU 40 to form an active slurrycatalyst in oil. A small amount of ammonium sulfate formed from thenickel sulfate and ammonia gas added to the CSU 40, is also present inthis stream. The small stream of water (stream 18) acts to keep thesmall amount of ammonium sulfate in solution. This preventsprecipitation in the equipments. The active slurry catalyst in oil(stream 21) enters into a catalyst preconditioning unit (CPU 50).Hydrogen enters the CPU 50 through stream 24.

The process conditions of the catalyst preconditioning unit (CPU 50)include temperature ranges from about 400° F. to about 1000° F.,preferably from about 500° to about 800° F., and most preferably fromabout 600° F. to about 700° F. Pressure ranges from about 100 to about3000 psi, preferably from 300 to about 2500 psi and more preferably fromabout 500 to about 2000 psi. The hydrogen rate is in the range from 2500to 7500 scf/bbl, preferably from 500 to 6000 scf/bbl. Preconditioning ofammonium sulfate into hydrogen sulfide and ammonia requires about 2hours. Residence time in the catalyst preconditioning unit (CPU) for themixture comprising oil, slurry and ammonium sulfate is from 1.5 to threehours, preferably about 2 hours.

For every mole of hydrogen sulfide gas produced in the catalystpreconditioning unit (CPU 50) unit, 2 moles of ammonia are produced.

The CPU 50 is a continuously stirred tank reactor (CSTR or alternately,perfectly mixed reactor). This type of reactor is employed in order toprevent catalyst agglomeration.

The residuum feedstock 2 to the process of the present invention isgenerally a high boiling hydrocarbonaceous material having a normalboiling range mostly above 600° F. often having a normal boiling pointrange wherein at least 80% v/v of the feed boils between 600° F. and1500° F., or between 800° F. and 1450° F. Residuum feedstocks usefullyprocessed in the present invention may contain more than 500 ppmasphaltenes or 1000 ppm asphaltenes, and may contain as much as 10,000ppm asphaltenes or more. The residuum feedstocks also usually containmore than 10 ppm metals and greater than 0.1% by weight sulfur, Themetals are betieved to be present as organometallic compounds, but theconcentrations of metals referred to herein are calculated as parts permillion pure metal. The contaminating metals in the feed typicallyinclude nickel, vanadium and iron The sulfur is present as organicsulfur compounds and the wt % sulfur is calculated based on elementalsulfur. Typical feedstocks for the present invention include deasphaltedresidua or crude, crude oil atmospheric distillation column bottoms(reduced crude oil or atmospheric column residuum), or vacuumdistillation column bottoms (vacuum residua).

EXAMPLE

Typical vacuum residuum feed properties are listed in the followingtable:

API gravity at 60/60 3.9 Sulfur (wt %) 5.58 Nitrogen (ppm) 5770 Nickel(ppm) 93 Vanadium (ppm) 243 Carbon (wt %) 83.57 Hydrogen (wt %) 10.04MCRT (wt %) 17.2 Viscosity @ 212° F. (cSt) 3727 Pentane Asphaltenes (wt%) 13.9 Fraction Boiling above 1050° F. (wt %) 81

Typical process conditions used for heavy oil upgrading are listed asfollowing

Total pressure (psig) 2500 Mo/Oil ratio (%) 1.5 LHSV 0.25 Reactortemperature (° F.) 700–725° F. H2 gas rate (SCF/B) 7500

Two batches of slurry catalyst streams obtained as described above weresent to the vacuum residuum hydrocracking (VRHU) unit for use ascatalysts The first batch was sent to the VRHU directly from thecatalyst synthesis unit or from storage, without preliminarypreconditioning.

The second batch was preconditioned in hydrogen as shown in the FIGUREprior to entering the VRHU.

Side by side comparison of VRHU performance results for conditionedslurry catalyst v. unconditioned slurry catalyst, are provided in thetable below:

Without With Preconditioning Preconditioning Hydrodenitrogenation: 80.5%89.4% Hydrodemetallization 97.2 98.6 Conversion of 1000 F. + 96.5 99.1fraction Conversion of 650 F. + 69.8 74.1 Fraction Conversion of 800F. + 88.3 91.8 Fraction

The improvement is approximately equivalent to increasing the freshcatalyst dosage to the VRHU by 30%.

1. A process for the hydroprocessing of heavy oils, having at least one reaction stage, said process comprising the following steps: (a) contacting a hydrocarbon feed stream under slurry hydroprocessing conditions with a hydrogen stream and a stream comprising slurry hydrocracking catalyst in a vacuum residuum slurry hydroprocessing unit, and recovering a product stream, along with a stream comprising spent slurry hydroprocessing catalyst and unconverted hydrocarbon feed; (b) passing the stream comprising spent slurry hydroprocessing catalyst and unconverted hydrocarbon feed to a deoiling unit, where it is combined with a solvent, products and gases then being recovered, as well as a stream comprising spent slurry catalyst; (c) passing the stream comprising spent slurry catalyst to a metals recovery unit, where it is contacted with an ammonium leach solution in order to recover ammonium sulfate and compounds comprising Group VIII and Group VIB metals; (d) passing the compounds comprising Group VIII and Group VIB metals to a catalyst synthesis unit, where they are contacted with ammonia, hydrogen sulfide gas, hydrocarbon stream, hydrogen and a small amount of water to create an active slurry catalyst in oil, the oil comprising ammonium sulfate (e) passing the effluent of step (d) into a preconditioning unit in order to increase the temperature and reduce shock on the slurry catalyst, wherein the effluent is contacted with hydrogen and is decomposed into hydrogen sulfide and ammonia, streams which are removed from the preconditioning unit; (f) passing the effluent for step (e), which comprises the active slurry catalyst in oil to storage or to a vacuum residuum slurry hydroprocessing unit.
 2. The process of claim 1, wherein water is added to the hydrocarbon feed stream prior to its entrance into the vacuum residuum slurry hydroprocessing unit.
 3. The process of claim 1, wherein slurry hydroprocessing conditions are selected from the group consisting of hydrocracking, hydrotreating, hydrodesulfurization, hydrodenitrification, and hydrodemetallization.
 4. The process of claim 3, where in the process is slurry hydrocracking.
 5. The process of claim 3, wherein the slurry hydrocracking process typically operates at a temperature of at least 800° F., with a hydrogen pressure from about 1500 psi to about 3500 psi.
 6. The process of claim 1, wherein hydrocarbon feedstocks which may be upgraded by slurry hydroprocessing have a normal boiling range above 600° F.
 7. The process of claim 1, in which the solvent employed in the deoiling unit, is toluene.
 8. The process of claim 1, wherein the stream comprising spent slurry catalyst is subjected to a series of solvent extractions and crystallization steps in the metals recovery unit in order to recover ammonium sulfate as well as compounds comprising Group VIII and Group VIB metals;
 9. The process of claim 8, wherein the Group VIII metal is nickel and the Group VIB metal is molybdenum.
 10. The process of claim 8, in which the Group VIII metal compound is nickel sulfate and the Group VIB metal compound, is molybdenum dimolybdate.
 11. The process of claim 1, wherein the hydrocarbon stream of step (b) comprises a light hydrocarbon or vacuum gas oil.
 12. The process of claim 1, wherein conditions in the catalyst synthesis unit comprise a temperature in the range from 80° F. to 200° F., preferably in the range from 100° F. to 180° F., and most preferably in the range from 130° F. to 160° F.
 13. The process of claim 1, wherein conditions in the catalyst synthesis unit comprise a pressure in the range from 100 to 3000 psig preferably in the range from 200 to 1000 psig, and most preferably from 300 to 500 psig.
 14. The process of claim 1, in which a small stream of water is added to the catalyst synthesis unit in order to prevent agglomeration of ammonium sulfate.
 15. The process of claim 1, wherein conditions in the preconditioning unit comprise a temperature in the range from about 400° F. to about 1000° F., preferably from about 500° to about 800° F., and most preferably from about 600° F. to about 700° F.
 16. The process of claim 1, wherein conditions in the preconditioning unit comprise a pressure in the range from about 100 to about 3000 psi, preferably from 300 to about 2500 psi and more preferably from about 500 to about 2000 psi.
 17. The process of claim 1, wherein the hydrogen flow rate in the preconditioning unit is in the range from 2500 to 7500 scf/bbl and preferably from 5000 to 6000 scf/bbl.
 18. The process of claim 1, in which the residence time in the preconditioning unit is from 1.5 to three hours, preferably about 2 hours.
 19. The process of claim 1, in which the preconditioning unit is a constant stirred tank reactor. 